Detection of early inter-radio access technology (irat) handover triggering

ABSTRACT

A device detects poor coverage associated with a source radio access technology (RAT) with which the device is connected, and connects to a target RAT. The device also measures the source RAT for a time period after connecting to the target RAT, and sends, based on the measurements, one or more measurement reports to the target RAT, where the target RAT forwards the one or more measurement reports to the source RAT. Alternatively, or additionally, the target RAT may detect that the handover was triggered too early and may inform the source RAT or command the UE to return to the source RAT. The device further stops the measuring and the sending when the time period expires. In this way, IRAT handover parameters may be automatically or manually tuned to minimize the number of handovers triggered too early, which may result in a more efficient cell configuration.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 13/792,769, filed Mar. 11, 2013, which itself is a continuationof U.S. patent application Ser. No. 12/766,148, filed Apr. 23, 2010, nowU.S. Pat. No. 8,417,244 the disclosure and content of both of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

Embodiments described herein relate generally to communication systems,and, more particularly, to detecting too early inter-radio accesstechnology (IRAT) handover triggering in a telecommunication system.

BACKGROUND

Specification of concepts associated with an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) (e.g., including conceptsassociated with Long Term Evolution (LTE) and System ArchitectureEvolution (SAE)) is currently ongoing within the 3rd GenerationPartnership Project (3GPP). It is envisioned that E-UTRAN will initiallyhave limited radio coverage. To provide seamless mobility, it isnecessary to handover (HO) user equipment (UEs) (e.g., mobilecommunication devices) in the E-UTRAN to an alternative RAT (e.g., suchas a Global System for Mobile communications (GSM) EDGE Radio AccessNetwork (GERAN) or a UTRAN) with better coverage. Generally, it is alsopreferred for a UE, served by a second generation (2G) network (e.g.,such as a GERAN) or a third generation (3G) network (e.g., such as aUTRAN), to switch to (e.g., via a handover) an E-UTRAN once the UE iswithin the coverage of the E-UTRAN. The E-UTRAN is preferred sincehigher data rates are offered by the E-UTRAN, which enables serviceswith greater bandwidth requirements. A handover between two differentRATs is referred to as an inter-RAT (IRAT) handover.

Network administrators are often responsible for multiple networks whichuse different RATs that cover overlapping areas at differentfrequencies. It is also common for at least one of the networks to covera wider area than other networks, especially at the early stages ofdeployment of new networks (e.g., such as E-UTRANs).

Moving between different RATs is a demanding process for both a UE and anetwork. On the UE side, measuring a RAT on a different frequencyrequires the UE to switch modes, which prevents the UE fromsending/receiving information to/from a connected RAT. In addition, whenperforming RAT measurements, the UE consumes more battery power thanduring normal operation. On the network side, scheduling needs to beadapted to the restrictions associated with the UE, which affectsnetwork efficiency. The restrictions associated with the UE and thenetwork may reduce an end user's experience due to higher latency, alower data rate, and/or a higher probability of dropped calls duringperformance of measurements.

If two or more networks have different RATs, a network administratorsets priorities between different networks in order to ensure that UEsconnect to the network with the highest performance (e.g., a networkwith a newest and least deployed RAT). The network administrator alsoattempts to ensure that when a UE moves from a network area not coveredby a source RAT, the UE experiences seamless mobility to a target RATwith overlapping coverage (e.g., a more established and deployed RAT).

A process for IRAT handover triggering from a first (source) RAT (e.g.,a LTE network) to a second (target) RAT (e.g., a Wideband Code DivisionMultiple Access (WCDMA) network) may include one or more of thefollowing steps. If a UE is connected to the first RAT and detects poorcoverage of the first RAT, the UE begins IRAT handover measurements anddetects the second RAT with good coverage. The UE reports the IRAThandover measurements to the first RAT network, and the first RATnetwork commands the UE to handover to the second RAT, after receivingan acknowledgement of an IRAT handover request. The UE connects to thesecond RAT network and sends a handover confirm message to the secondRAT network. The second RAT network sends a handover success report tothe first RAT network.

One parameter that needs to be controlled (e.g., when triggering an IRAThandover) is an absolute threshold that defines when the first RATcoverage is becoming poor and IRAT handover measurements are needed. Ifthe setting of this threshold is not optimal, an end user's experiencemay be degraded. For example, if the IRAT handover measurement istriggered too late, the UE may not be able to report the IRAT handovermeasurements to the first RAT network or may not be able to receive thehandover command due to a heavily degraded connection with the first RAT(e.g., resulting in a radio link failure). If the IRAT handovermeasurements are triggered too early, the UE may not find a second RATnetwork with good coverage or the first RAT network coverage may recoversoon after the IRAT handover measurement was triggered. In both cases,the IRAT handover measurement will not be used for any purpose, ahandover to a lower priority RAT may be unnecessarily triggered, or thecall would be dropped (e.g., due to the more demanding task of measuringother RATs while maintaining a connection with a serving RAT) resultingin an inefficient use of the networks.

In an early stage of network deployment, coverage is provided only inhot-spots and it is important to permit UEs to move to a lower prioritynetwork with wider coverage (e.g., the IRAT handover measurements aretriggered as soon as poor coverage is detected). As new networks aredeployed, full coverage may be provided in most areas and it isimportant to ensure that IRAT handover is triggered only in edge cells(e.g., cells in the middle of a coverage area will not need to triggerIRAT handover). In some instances, cells may initially provide coveragein a hot spot, and, as the network deployment develops, the cells mayend up being located far from the edges of the network. Since optimizingvalues of the IRAT handover parameters (e.g., per cell) is an expensiveprocess, it is typical that default parameters are used for an entirelife cycle of a cell.

In order to avoid radio link failure, network administrators often setrequirements on RAT coverage too high (e.g., the threshold defining poorcoverage for a RAT may be set to a too restrictive value), resulting intoo early IRAT handover triggering and inefficient use of the network.Typically, it is safer to trigger the IRAT handover too early, ratherthan too late, because triggering the IRAT handover too late results inradio link failure.

Setting requirements on RAT coverage in such a manner may be beneficialfor cells partially covering areas that need several RATs in order toprovide full coverage. However, setting requirements on RAT coverage toohigh leads to an inefficient use of a highest priority network forcentrally-located cells (e.g., where IRAT handover is unnecessary)because a UE that is handed over to a lower priority RAT will in mostcases not return to the highest priority RAT until poor coverage isdetected or until the UE enters an idle mode (e.g., via cellreselection).

This situation may be corrected (e.g., manually or automatically) bylowering the poor coverage threshold on cells experiencing too earlyIRAT handover triggering. However, detection of a too high coveragethreshold is not currently possible. For example, a network may includetwo LTE cells (e.g., cell LTE-A and cell LTE-B). Cell LTE-A may be aborder cell and may include optimal settings for IRAT handovertriggering. When coverage of cell LTE-A falls below a threshold, UEs maybe handed over to WCDMA network in a seamless manner. Cell LTE-B may bea center cell and may include a poor coverage threshold that is set toohigh. When coverage of cell LTE-B temporarily drops, UEs may be handedover to the WCDMA network unnecessarily. If the poor coverage thresholdwas set lower, the UEs would continue in cell LTE-B without any negativeeffects.

In this example, both cells (e.g., cell LTE-A and cell LTE-B) experiencenormal operation, no radio link failure occurs, and every IRAT handoveris successfully completed. Currently, however, there is no mechanism forcell LTE-A to verify that it was a good decision to handover the UEs tothe WCDMA network, and there is no mechanism for cell LTE-B to determinethat the handovers of the UEs to the WCDMA network were triggered tooearly. As a consequence, no manual and/or automatic tuning can beperformed.

SUMMARY

It is an object of the invention to overcome at least some of the abovedisadvantages, and to provide systems and/or methods for detecting IRAThandovers that are triggered too early in a telecommunication system.

An embodiment described herein may provide a method in a network thatincludes a user equipment. The method may include detecting, by the userequipment, poor coverage associated with a source radio accesstechnology (RAT) with which the user equipment is connected, andconnecting the user equipment to a target RAT when the poor coverage isdetected. The method may also include measuring, by the user equipment,the source RAT for a time period after the user equipment connects tothe target RAT, and sending, by the user equipment and based on themeasurements, one or more measurement reports to the target RAT.

Another embodiment described herein may provide a user equipment in anetwork. The user equipment may include a memory to store a plurality ofinstructions, and a processor to execute instructions in the memory todetect poor coverage associated with a source radio access technology(RAT) with which the user equipment is connected, and connect the userequipment to a target RAT when the poor coverage is detected. Theprocessor may further execute instructions in the memory to measure thesource RAT for a time period after the user equipment connects to thetarget RAT, and send, based on the measurements, one or more measurementreports to the target RAT.

Still another embodiment described herein may provide a method in anetwork that includes a user equipment connected to a source radioaccess technology (RAT), where the user equipment connects to a targetRAT when poor coverage is detected in the source RAT. The method mayinclude instructing the user equipment to measure at least one of asignal strength and/or a signal quality associated with the source RATfor a time period after the user equipment connects to the target RAT;instructing the user equipment to send, based on the measurements, oneor more measurement reports to the target RAT; and determining, by thesource RAT, whether an inter-RAT (IRAT) handover to the target RAT wastriggered too early.

A further embodiment described herein may provide a method in a networkthat includes a user equipment connected to a source radio accesstechnology (RAT), where the user equipment connects to a target RAT whenpoor coverage is detected in the source RAT. The method may includeinstructing the user equipment to measure at least one of a signalstrength and/or a signal quality associated with the source RAT for atime period after the user equipment connects to the target RAT, andreceiving, by the target RAT and from the user equipment, one or moremeasurement reports generated based on the measurements.

Still a further embodiment described herein may provide A device in asource radio access technology (RAT) connected to a user equipment,where the user equipment connects to a target RAT when poor coverage isdetected in the source RAT. The device may include a memory to store aplurality of instructions, and a processor to execute instructions inthe memory to: instruct the user equipment to measure at least one of asignal strength and/or a signal quality associated with the source RATfor a time period after the user equipment connects to the target RAT,instruct the user equipment to send, based on the measurements, one ormore measurement reports to the target RAT, and determine whether aninter-RAT (IRAT) handover to the target RAT was triggered too early.

Another embodiment described herein may provide a device in a targetradio access technology (RAT) connected to a user equipment, where theuser equipment connects to a target RAT when a problem occurs in asource RAT. The device may include a memory to store a plurality ofinstructions; and a processor to execute instructions in the memory to:instruct the user equipment to measure at least one of a signal strengthand/or a signal quality associated with the source RAT for a time periodafter the user equipment connects to the target RAT, and receive, fromthe user equipment, one or more measurement reports generated based onthe measurements.

Systems and/or methods described herein may provide mechanisms to detecttoo early IRAT handover triggering (e.g., which was previouslyundetectable) and to mitigate too early IRAT handover triggering in thefuture. The systems and/or methods may enable automatic or manual tuningof IRAT handover parameters to minimize the number of handoverstriggered too early, which may result in a more efficient cellconfiguration. The systems and/or methods may, for example, instruct aUE (e.g., for which an IRAT handover, from a source RAT to a target RAT,was triggered) to continue measuring the source RAT and the target RATfor a time period after the IRAT handover. The systems and/or methodsmay instruct the UE to send a measurement report (e.g., based on themeasurements of the source and target RATs) to the target RAT after thetime period expires. Upon reception of the measurement report, thetarget RAT may forward the measurement report to the source RAT.Alternatively, or additionally, the target RAT may trigger a second IRAThandover to the source RAT even if a poor coverage threshold (e.g., fortriggering IRAT handover) is not satisfied. The source RAT may detectthat the IRAT handover was triggered too early based on the UE returningto the source RAT. In another alternative, the target RAT may detectthat the IRAT handover was triggered too early and may send a too earlyIRAT handover indication to the source RAT.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example network in which systems and/ormethods described herein may be implemented;

FIG. 2 is a diagram of example components of a network node shown inFIG. 1;

FIG. 3 is a diagram of alternative example components of a network nodeshown in FIG. 1;

FIG. 4 is a diagram of example components of a user equipment depictedin FIG. 1;

FIG. 5 is a diagram of example interactions among components of anexample portion of the network depicted in FIG. 1;

FIG. 6 is a diagram of further example interactions among components ofan example portion of the network depicted in FIG. 1;

FIG. 7 is a diagram of additional example interactions among componentsof an example portion of the network depicted in FIG. 1;

FIGS. 8 and 9 are flow charts of an example process for detecting tooearly IRAT handover triggering in a telecommunication system accordingto embodiments described herein;

FIG. 10 is a flow chart of another example process for detecting tooearly IRAT handover triggering in a telecommunication system accordingto embodiments described herein; and

FIG. 11 is a flow chart of still another example process for detectingtoo early IRAT handover triggering in a telecommunication systemaccording to embodiments described herein.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings.The same reference numbers in different drawings may identify the sameor similar elements. Also, the following detailed description does notlimit the invention.

FIG. 1 is a diagram of an example network 100 in which systems and/ormethods described herein may be implemented. As shown, network 100 mayinclude a UE 110, a source RAT 120 that includes a network node 122, andtarget RAT 130 that includes a network node 132. A single UE 110, asingle source RAT 120, a single target RAT 130, and two network nodes122/132 have been illustrated in FIG. 1 for simplicity. In practice,there may be more UEs 110, source RATs 120, network nodes 122, targetRATs 130, and/or network nodes 132. Also, in some instances, one or moreof the components of network 100 may perform one or more functionsdescribed as being performed by another one or more of the components ofnetwork 100.

UE 110 may include one or more computation and/or communication devicescapable of sending/receiving voice and/or data to/from other UEs and/ornetwork nodes 122/132. UE 110 may include, for example, aradiotelephone, a personal communications system (PCS) terminal (e.g.,that may combine a cellular radiotelephone with data processing and datacommunications capabilities), a personal digital assistant (PDA) (e.g.,that can include a radiotelephone, a pager, Internet/intranet access,etc.), a laptop computer, a tablet computer, etc.

Source RAT 120 may be part of a mobile telecommunication system (e.g.,network 100) and may implement a particular radio access technology.Source RAT 120 may include a collection of network nodes (e.g., networknode 122), such as radio network controllers (RNCs) and base stations(also referred to as NodeBs or eNodeBs). Source RAT 120 may carry manytraffic types, from real-time circuit switched traffic to Internetprotocol (IP)-based packet switched traffic. Source RAT 120 may permitconnectivity between UE 110 and a core network (not shown). In oneembodiment, source RAT 120 may implement a radio access technology(e.g., LTE) that is different than a radio access technology implementedby target RAT 130. In one example, UE 110 may initially be connected tosource RAT 120, but may perform an IRAT handover to target RAT 130.

Network node 122 may include one or more devices that receive voiceand/or data from a core network (not shown) and transmit that voiceand/or data to UE 110 via an air interface. Network node 122 may alsoinclude one or more devices that receive voice and/or data from UE 110over an air interface and transmit that voice and/or data to other UEs110, other network nodes of source RAT 120, and/or the core network. Inone embodiment, network node 122 may form one or more cells (e.g., innetwork 100) that may provide service to one or more UEs 110. In oneexample, network node 122 may correspond to a RNC. The RNC may act as acontrolling radio network controller (CRNC), a drift radio networkcontroller (DRNC), or a serving radio network controller (SRNC). A CRNCmay be responsible for controlling the resources of a base station. Onthe other hand, an SRNC may serve particular UEs 110 and may manageconnections towards those UEs 110. Likewise, a DRNC may fulfill asimilar role to the SRNC (e.g., may route traffic between a SRNC and aparticular UE 110). In another example, network node 122 may correspondto or include a base station.

Target RAT 130 may be part of a mobile telecommunication system (e.g.,network 100) and may implement a particular radio access technology.Target RAT 130 may include a collection of network nodes (e.g., networknode 132), such as RNCs and base stations. Target RAT 130 may carry manytraffic types, from real-time circuit switched traffic to IP-basedpacket switched traffic. Target RAT 130 may permit connectivity betweenUE 110 and a core network (not shown). In one embodiment, target RAT 130may implement a radio access technology (e.g., WCDMA) that is differentthan a radio access technology implemented by source RAT 120.

Network node 132 may include one or more devices that receive voiceand/or data from a core network (not shown) and transmit that voiceand/or data to UE 110 via an air interface. Network node 132 may alsoinclude one or more devices that receive voice and/or data from UE 110over an air interface and transmit that voice and/or data to other UEs110, other network nodes of target RAT 130, and/or the core network. Inone embodiment, network node 132 may form one or more cells (e.g., innetwork 100) that may provide service to one or more UEs 110. In oneexample, network node 122 may correspond to a RNC. The RNC may act as aCRNC, a DRNC, or a SRNC. In another example, network node 132 maycorrespond to a base station.

Although FIG. 1 shows example components of network 100, in otherembodiments, network 100 may include fewer components, differentcomponents, differently arranged components, or additional componentsthan depicted in FIG. 1. For example, network 100 may include many RATs,but UE 110 may move between a single source RAT 120 and a single targetRAT 130.

FIG. 2 is a diagram of example components of a network node (e.g.,network node 122 or 132) when network node 122/132 corresponds to a RNC.As shown in FIG. 2, network node 122/132 may include a processing system210, an Iub interface 220, an Iur interface 230, and/or other interfaces240.

Processing system 210 may control the operation of network node 122/132.As illustrated, processing system 210 may include a processing unit 212and a memory 214. Processing unit 212 may handle protocol exchangesbetween Iub interface 220, Iur interface 230, and other interfaces 240.In addition, processing unit 212 may generate control messages and/ordata messages and transmit those control messages and/or data messagesvia interfaces 220-240. Processing unit 212 may also process controlmessages and/or data messages received from interfaces 220-240. In oneembodiment, processing unit 212 may include one or more processors,microprocessors, application specific integrated circuits (ASICs), fieldprogrammable gate arrays (FPGAs), or the like. Memory 214 may include arandom access memory (RAM), a read-only memory (ROM), and/or anothertype of memory to store data and instructions that may be used byprocessing unit 212.

Iub interface 220 may include one or more line cards that allow networknode 122/132 to transmit control messages and/or data messages to andreceive control messages and/or data messages from base stations. Iurinterface 230 may include one or more line cards that allow network node122/132 to transmit control messages and/or data messages to and receivecontrol messages and/or data messages from other RNCs. Other interfaces240 may include interfaces to other devices and/or networks. Forexample, other interfaces 240 may include an Iu-cs interface, which is acore network interface to a circuit-switched voice network, and an Iu-psinterface, which is a core network interface to a packet-switched datanetwork.

As described herein, network node 122/132 may perform certain operationsin response to processing unit 212 executing software instructions of anapplication contained in a computer-readable medium, such as memory 214.A computer-readable medium may be defined as a physical or logicalmemory device. A logical memory device may include memory space within asingle physical memory device or spread across multiple physical memorydevices. The software instructions may be read into memory 214 fromanother computer-readable medium or from another device. The softwareinstructions contained in memory 214 may cause processing unit 212 toperform processes described herein. Alternatively, hardwired circuitrymay be used in place of or in combination with software instructions toimplement processes described herein. Thus, embodiments described hereinare not limited to any specific combination of hardware circuitry andsoftware.

Although FIG. 2 shows example components of network node 122/132, inother embodiments, network node 122/132 may contain fewer components,different components, differently arranged components, or additionalcomponents than depicted in FIG. 2. Additionally or alternatively, oneor more components of network node 122/132 may perform one or more othertasks described as being performed by one or more other components ofnetwork node 122/132.

FIG. 3 is a diagram of example components of a network node (e.g.,network node 122 or 132) when network node 122/132 corresponds to a basestation. As shown in FIG. 3, network node 122/132 may include antennas310, transceivers (TX/RX) 320, a processing system 330, and an Iubinterface (I/F) 340.

Antennas 310 may include one or more directional and/or omni-directionalantennas. Transceivers 320 may be associated with antennas 310 and mayinclude transceiver circuitry for transmitting and/or receiving symbolsequences in a network, such as network 100, via antennas 310.

Processing system 330 may control the operation of network node 122/132.Processing system 330 may also process information received viatransceivers 320 and Iub interface 340. Processing system 330 mayfurther measure quality and strength of a connection, may determine thedistance to UEs 110, and may transmit this information to other networknodes. As illustrated, processing system 330 may include a processingunit 332 and a memory 334.

Processing unit 332 may include one or more processors, microprocessors,ASICs, FPGAs, or the like. Processing unit 332 may process informationreceived via transceivers 320 and Iub interface 340. The processing mayinclude, for example, data conversion, forward error correction (FEC),rate adaptation, WCDMA spreading/dispreading, quadrature phase shiftkeying (QPSK) modulation, etc. In addition, processing unit 332 maytransmit control messages and/or data messages, and may cause thosecontrol messages and/or data messages to be transmitted via transceivers320 and/or Iub interface 340. Processing unit 332 may also processcontrol messages and/or data messages received from transceivers 320and/or Iub interface 340.

Memory 334 may include a RAM, a ROM, and/or another type of memory tostore data and instructions that may be used by processing unit 332.

Iub interface 340 may include one or more line cards that allow networknode 122/132 to transmit data to and receive data from other devices innetwork 100.

As described herein, network node 122/132 may perform certain operationsin response to processing unit 332 executing software instructions of anapplication contained in a computer-readable medium, such as memory 334.The software instructions may be read into memory 334 from anothercomputer-readable medium or from another device via antennas 310 andtransceivers 320. The software instructions contained in memory 334 maycause processing unit 332 to perform processes described herein.Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes describedherein. Thus, embodiments described herein are not limited to anyspecific combination of hardware circuitry and software.

Although FIG. 3 shows example components of network node 122/132, inother embodiments, network node 122/132 may contain fewer components,different components, differently arranged components, or additionalcomponents than depicted in FIG. 3. Additionally or alternatively, oneor more components of network node 122/132 may perform one or more othertasks described as being performed by one or more other components ofnetwork node 122/132.

FIG. 4 is a diagram of example components of UE 110. As shown, UE 110may include a processor 400, a memory 410, a user interface 420, acommunication interface 430, and an antenna assembly 440.

Processor 400 may include one or more microprocessors, ASICs, FPGAs, orthe like. Processor 200 may control operation of UE 110 and itscomponents. In one embodiment, processor 200 may control operation ofcomponents of UE 110 in a manner described herein.

Memory 410 may include a RAM, a ROM, and/or another type of memory tostore data and instructions that may be used by processor 400.

User interface 420 may include mechanisms for inputting information toUE 110 and/or for outputting information from UE 110. Examples of inputand output mechanisms might include buttons (e.g., control buttons, keysof a keypad, a joystick, etc.) or a touch screen interface to permitdata and control commands to be input into UE 110; a speaker to receiveelectrical signals and output audio signals; a microphone to receiveaudio signals and output electrical signals; a display to output visualinformation (e.g., text input into UE 110); a vibrator to cause UE 110to vibrate; etc.

Communication interface 430 may include, for example, a transmitter thatmay convert baseband signals from processor 400 to radio frequency (RF)signals and/or a receiver that may convert RF signals to basebandsignals. Alternatively, communication interface 430 may include atransceiver to perform functions of both a transmitter and a receiver.Communication interface 430 may connect to antenna assembly 440 fortransmission and/or reception of the RF signals.

Antenna assembly 440 may include one or more antennas to transmit and/orreceive RF signals over the air. Antenna assembly 440 may, for example,receive RF signals from communication interface 430 and transmit themover the air, and receive RF signals over the air and provide them tocommunication interface 430. In one embodiment, for example,communication interface 430 may communicate with a network and/ordevices connected to a network.

As will be described in detail below, UE 110 may perform certainoperations described herein in response to processor 400 executingsoftware instructions of an application contained in a computer-readablemedium, such as memory 410. The software instructions may be read intomemory 410 from another computer-readable medium or from another devicevia communication interface 430. The software instructions contained inmemory 410 may cause processor 400 to perform processes describedherein. Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes describedherein. Thus, embodiments described herein are not limited to anyspecific combination of hardware circuitry and software.

Although FIG. 4 shows example components of UE 110, in otherembodiments, UE 110 may contain fewer components, different components,differently arranged components, or additional components than depictedin FIG. 4. Additionally or alternatively, one or more components of UE110 may perform one or more other tasks described as being performed byone or more other components of UE 110.

FIG. 5 is a diagram of example interactions among components of anexample portion 500 of network 100. As shown, example network portion500 may include UE 110, source RAT 120, and target RAT 130. UE 110,source RAT 120, and/or target RAT 130 may include the features describedabove in connection with one or more of FIGS. 1-4. In one example,source RAT 120 may correspond to network node 122 and target RAT 130 maycorrespond to network node 132. In one embodiment, FIG. 5 may depict afirst mechanism for detecting whether an IRAT handover (e.g., fromsource RAT 120 to target RAT 130) was triggered too early. The firstmechanism may include UE 110 performing a backward measurement of sourceRAT 120 for a period of time after UE 110 is connected to target RAT130.

As further shown in FIG. 5, UE 110 may initially be connected to sourceRAT 120 and may detect poor coverage in source RAT 120, as indicated byreference number 505. UE 110 may begin searching (e.g., viameasurements) for a target RAT with better coverage than source RAT 120,as indicated by reference number 510, and may identify target RAT 130based on the measurements. UE 110 may provide a measurement report(e.g., identifying target RAT 130 as a RAT with better coverage thansource RAT 120) to source RAT 120, as indicted by reference number 515.Source RAT 120 may receive the measurement report and may generate anIRAT handover request (e.g., requesting handover of UE 110 to target RAT130) based on the measurement report. Source RAT 120 may provide theIRAT handover request to target RAT 130, as indicated by referencenumber 520, and may receive (e.g., based on the IRAT handover request)an IRAT handover request acknowledgment from target RAT 130, asindicated by reference number 525.

Based on the IRAT handover request acknowledgment, source RAT 120 maytrigger an IRAT handover of UE 110 (e.g., to target RAT 130), asindicated by reference number 530, and may provide an IRAT handovercommand to UE 110, as indicated by reference number 535. Based on theIRAT handover command, UE 110 may connect to target RAT 130, asindicated by reference number 540. UE 110 may measure coverageassociated with source RAT 120 for a period of time (e.g., which may bedefined by a network administrator) after UE 110 is connected to targetRAT 130, as indicated by reference number 545.

As further shown in FIG. 5, UE 110 may provide a measurement report totarget RAT 130, as indicated by reference number 550. The measurementreport may be provided (e.g., by UE 110 to target RAT 130) together witha handover confirm message, as further indicated by reference number550. Target RAT 130 may receive the measurement report and may forwardthe measurement report to source RAT 120 (e.g., along with handoversuccess message), as indicated by reference number 555. UE 110 maycontinue (e.g., for the period of time) to provide one or moreadditional measurement reports to target RAT 130, as indicated byreference number 560, and target RAT 130 may forward the one of moreadditional measurement reports to source RAT 120, as indicated byreference number 565. After the period of time expires, UE 110 may stopmeasuring and/or reporting about the coverage associated with source RAT120, as indicated by reference number 570. In one example, UE 110 maystop measuring and/or reporting (e.g., before the time period expires)if no signal is received from source RAT 120.

Source RAT 120 may receive the one or more measurement reports, and maycompare the measurement report(s) to one or both of strength/quality(e.g., a signal strength and/or a signal quality) thresholds. If themeasured signal strength and/or signal quality of source RAT 120 (e.g.,as provided by the measurement report(s)) satisfies the strength/qualitythresholds after IRAT handover of UE 110 to target RAT 130, source RAT120 may determine that the IRAT handover was performed too early. Basedon this determination, IRAT handover parameters may be automatically ormanually tuned to minimize the number of handovers triggered too early,which may result in a more efficient cell configuration.

Although FIG. 5 shows example components of network portion 500, inother embodiments, network portion 500 may contain fewer components,different components, differently arranged components, or additionalcomponents than depicted in FIG. 5. Additionally or alternatively, oneor more components of network portion 500 may perform one or more othertasks described as being performed by one or more other components ofnetwork portion 500.

FIG. 6 is a diagram of further example interactions among components ofan example portion 600 of network 100. As shown, example network portion600 may include UE 110, source RAT 120, and target RAT 130. UE 110,source RAT 120, and/or target RAT 130 may include the features describedabove in connection with one or more of FIGS. 1-4. In one example,source RAT 120 may correspond to network node 122 and target RAT 130 maycorrespond to network node 132. In one embodiment, FIG. 6 may depict asecond mechanism for detecting whether an IRAT handover (e.g., fromsource RAT 120 to target RAT 130) was triggered too early. The secondmechanism may include UE 110 performing a backward measurement of sourceRAT 120 for a period of time after UE 110 is connected to target RAT130, and target RAT 130 triggering an IRAT handover back to source RAT120.

As further shown in FIG. 6, UE 110 may initially be connected to sourceRAT 120 and may detect poor coverage in source RAT 120, as indicated byreference number 605. UE 110 may begin searching (e.g., viameasurements) for a target RAT with better coverage than source RAT 120,as indicated by reference number 610, and may identify target RAT 130based on the measurements. UE 110 may provide a measurement report(e.g., identifying target RAT 130 as a RAT with better coverage thansource RAT 120) to source RAT 120, as indicted by reference number 615.Source RAT 120 may receive the measurement report and may generate anIRAT handover request (e.g., requesting handover of UE 110 to target RAT130) based on the measurement report. Source RAT 120 may provide theIRAT handover request to target RAT 130, as indicated by referencenumber 620. The IRAT handover request may include one or both ofstrength/quality thresholds (e.g., signal strength and/or signal qualitythresholds) for source RAT 120. In one example, one or both of thestrength/quality thresholds may be sent in a message that is separatefrom the IRAT handover request. In another example, one or both of thestrength/quality threshold(s) may not be sent for every IRAT handoverand may be stored in target RAT 130. The strength/quality thresholds mayprovide, for example, a minimum threshold on the signal strength and/orsignal quality received from source RAT 120 (e.g., by UE 110). SourceRAT 120 may receive (e.g., based on the IRAT handover request) an IRAThandover request acknowledgment from target RAT 130, as indicated byreference number 625.

Based on the IRAT handover request acknowledgment, source RAT 120 maytrigger an IRAT handover of UE 110 (e.g., to target RAT 130), asindicated by reference number 630, and may provide an IRAT handovercommand to UE 110, as indicated by reference number 635. Based on theIRAT handover command, UE 110 may connect to target RAT 130, asindicated by reference number 640.

In one embodiment, and as further shown in FIG. 6, UE 110 may measurecoverage associated with source RAT 120 for a period of time (e.g.,which may be defined by a network administrator) after UE 110 isconnected to target RAT 130, as indicated by reference number 645. UE110 may provide a measurement report (e.g., based on the measurements)to target RAT 130, as indicated by reference number 650. The measurementreport may be provided (e.g., by UE 110 to target RAT 130) together witha handover confirm message, as further indicated by reference number650. UE 110 may continue (e.g., for the period of time) to provide oneor more additional measurement reports to target RAT 130.

Target RAT 130 may receive the one or more measurement reports, and maycompare the measurement report(s) to one or both of the strength/quality(e.g., a signal strength and/or a signal quality) thresholds receivedfrom source RAT 120. If the measured signal strength and/or signalquality of source RAT 120 (e.g., as provided by the measurementreport(s)) satisfies the strength/quality thresholds after IRAT handoverof UE 110 to target RAT 130, target RAT 130 may determine that the IRAThandover was performed too early. Based on this determination, targetRAT 130 may trigger IRAT handover of UE 110 back to source RAT 120, asindicated by reference number 655. In one embodiment, IRAT handover ofUE 110 back to source RAT 120 (e.g., to the same or a different networknode of source RAT 120) may be triggered independently of astrength/quality level of target RAT 130. Target RAT 130 (e.g., aftersending a handover request and receiving an acknowledgement from sourceRAT 120) may provide a handover command to UE 110, as indicated byreference number 660, and UE 110 may stop measuring and/or reportingabout the coverage associated with source RAT 120 (e.g., afterexpiration of the time period). UE 110 may then connect to source RAT120 (e.g., based on the handover command), as indicated by referencenumber 665. The receiving network node of source RAT 120 may inform anetwork node in source RAT 120 (e.g., responsible for statisticcollection and optimization) that an IRAT handover was triggered tooearly, as indicated by reference number 670. IRAT handover parameters,associated with source RAT 120, may be automatically or manually tunedto minimize the number of handovers triggered too early, which mayresult in a more efficient cell configuration.

In an alternative embodiment, after successful IRAT handover andcontinued IRAT measurements, target RAT 130 may perform an analysis ofthe measurement report(s). If a signal/quality measurement of source RAT120 satisfies one or both of the strength/quality thresholds (e.g.,provided as indicated by reference number 620), target RAT 130 maytrigger an IRAT handover back to source RAT 120. Alternatively, if thestrength/quality thresholds are not provided to target RAT 130 (e.g., asindicated by reference number 620), target RAT 130 may use a generalthreshold on received signal strength/quality for IRAT handover fromtarget RAT 130 back to source RAT 120. Target RAT 130 may provide ahandover command to UE 110, and UE 110 may connect to source RAT 120(e.g., based on the handover command). In one example, UE 110 may bereturned back to source RAT 120 independently of whether astrength/quality measurement associated with target RAT 130 is above orbelow a general threshold to start IRAT measurement. In another example,the early handover from source RAT 120 to target RAT 130 may be detected(e.g., by source RAT 120) using statistics based on a ratio of returnedUEs 110 in source RAT 120.

Although FIG. 6 shows example components of network portion 600, inother embodiments, network portion 600 may contain fewer components,different components, differently arranged components, or additionalcomponents than depicted in FIG. 6. Additionally or alternatively, oneor more components of network portion 600 may perform one or more othertasks described as being performed by one or more other components ofnetwork portion 600. For example, in order to reduce a number ofmessages sent from target RAT 130 to source RAT 120, measurements maycollected and statistically processed in target RAT 130 rather than sentto source RAT 120 for collection and statistical processing.

FIG. 7 is a diagram of additional example interactions among componentsof an example portion 700 of network 100. As shown, example networkportion 700 may include UE 110, source RAT 120, and target RAT 130. UE110, source RAT 120, and/or target RAT 130 may include the featuresdescribed above in connection with one or more of FIGS. 1-4. In oneexample, source RAT 120 may correspond to network node 122 and targetRAT 130 may correspond to network node 132. In one embodiment, FIG. 7may depict a third mechanism for detecting whether an IRAT handover(e.g., from source RAT 120 to target RAT 130) was triggered too early.The third mechanism may include UE 110 performing a backward measurementof source RAT 120 for a period of time after UE 110 is connected totarget RAT 130, and target RAT 130 detecting and reporting the too earlyIRAT handover.

As further shown in FIG. 7, UE 110 may initially be connected to sourceRAT 120 and may detect poor coverage in source RAT 120, as indicated byreference number 705. UE 110 may begin searching (e.g., viameasurements) for a target RAT with better coverage than source RAT 120,as indicated by reference number 710, and may identify target RAT 130based on the measurements. UE 110 may provide a measurement report(e.g., identifying target RAT 130 as a RAT with better coverage thansource RAT 120) to source RAT 120, as indicted by reference number 715.Source RAT 120 may receive the measurement report and may generate anIRAT handover request (e.g., requesting handover of UE 110 to target RAT130) based on the measurement report. Source RAT 120 may provide theIRAT handover request to target RAT 130, as indicated by referencenumber 720. The IRAT handover request may include one or both ofstrength/quality thresholds (e.g., a signal strength and/or a signalquality threshold) for source RAT 120. As indicated above, thestrength/quality thresholds may provide, for example, a minimumthreshold on the signal strength and/or signal quality received fromsource RAT 120 (e.g., by UE 110). Source RAT 120 may receive (e.g.,based on the IRAT handover request) an IRAT handover requestacknowledgment from target RAT 130, as indicated by reference number725.

Based on the IRAT handover request acknowledgment, source RAT 120 maytrigger an IRAT handover of UE 110 (e.g., to target RAT 130), asindicated by reference number 730, and may provide an IRAT handovercommand to UE 110, as indicated by reference number 735. Based on theIRAT handover command, UE 110 may connect to target RAT 130, asindicated by reference number 740.

In one embodiment, and as further shown in FIG. 7, UE 110 may measurecoverage associated with source RAT 120 for a period of time (e.g.,which may be defined by a network administrator) after UE 110 isconnected to target RAT 130, as indicated by reference number 745. UE110 may provide a measurement report (e.g., based on the measurements)to target RAT 130, as indicated by reference number 750. The measurementreport may be provided (e.g., by UE 110 to target RAT 130) together witha handover confirm message, as further indicated by reference number750. UE 110 may continue (e.g., for the period of time) to provide oneor more additional measurement reports to target RAT 130.

Target RAT 130 may receive the one or more measurement reports, and maycompare the measurement report(s) to one or both of the strength/quality(e.g., a signal strength and/or a signal quality) thresholds receivedfrom source RAT 120. If the measured signal strength and/or signalquality of source RAT 120 (e.g., as provided by the measurementreport(s)) satisfies one or both of the strength/quality thresholdsafter IRAT handover of UE 110 to target RAT 130, target RAT 130 maydetermine that the IRAT handover was performed too early. Based on thisdetermination, target RAT 130 may generate a too early IRAT handoverindication, as indicated by reference number 755, and may provide thetoo early IRAT handover indication to source RAT 120, as indicated byreference number 760. UE 110 may stop measuring and reporting coverageassociated with source RAT 120 (e.g., after expiration of the timeperiod). Based on the too early IRAT handover indication, IRAT handoverparameters in source RAT 120 may be automatically or manually tuned tominimize the number of handovers triggered too early, which may resultin a more efficient cell configuration.

In an alternative embodiment, after successful IRAT handover andcontinued IRAT measurements, target RAT 130 may perform an analysis ofthe measurement report(s). If a signal/quality measurement of source RAT120 satisfies one or both the strength/quality thresholds (e.g.,provided as indicated by reference number 720), target RAT 130 mayinform source RAT 120 that the triggered IRAT handover was triggered tooearly (e.g., via a message sent by a transport network). Alternatively,if the strength/quality thresholds are not provided to target RAT 130(e.g., as indicated by reference number 720), target RAT 130 may use ageneral threshold on received signal strength/quality for IRAT handoverfrom target RAT 130 back to source RAT 120. In one example, the earlyhandover from source RAT 120 to target RAT 130 may be detected (e.g., bysource RAT 120) using statistics based on a ratio of received too earlyhandover messages from target RAT 130.

Although FIG. 7 shows example components of network portion 700, inother embodiments, network portion 700 may contain fewer components,different components, differently arranged components, or additionalcomponents than depicted in FIG. 7. Additionally or alternatively, oneor more components of network portion 700 may perform one or more othertasks described as being performed by one or more other components ofnetwork portion 700. For example, in order to reduce a number ofmessages sent from target RAT 130 to source RAT 120, measurements maycollected and statistically processed in target RAT 130 rather than sentto source RAT 120 for collection and statistical processing.

The three mechanisms described above in connection with FIGS. 5-7 mayprovide reliable information to source RAT 120 as to whether an IRAThandover decision was correctly made or made too early. The firstmechanism (FIG. 5) may provide such reliable information by sending amessage (e.g., via a transport or core network) containing informationabout a status of measurements after handover. The second mechanism(FIG. 6) may provide such reliable information in a similar manner, butmay also command UE 110 to return to source RAT 120. Source RAT 120 mayinterpret the return of UE 110 (e.g., to source RAT 120) as anindication of a too early IRAT handover. Since the return IRAT handoverof UE 110 can be provided to a same or a different network node as theoriginal network node (e.g., of source RAT 120), additional inter-nodecommunication may be performed in source RAT 120 in order to determinethe too early IRAT handover. The third mechanism (FIG. 7) may follow asimilar approach as the second mechanism, but instead of triggering thesecond IRAT handover (e.g., back to source RAT 120), target RAT 130 maysend a too early handover indication to source RAT 120.

In all three mechanisms, by computing all or a known subset of IRAThandovers, source RAT 120 may calculate a too early IRAT handover (HO)ratio, for example, as follows:

${{Early\_ IRAT}{\_ HO}{\_ Ratio}} = {\frac{{Number\_ Too}{\_ Early}{\_ IRAT}{\_ HO}}{{Number\_ Triggered}{\_ IRAT}{\_ HO}}.}$

The too early IRAT handover ratio may be calculated per source cell(e.g., of source RAT 120) or per cell relation. The too early IRAThandover ratio may provide a good indication of how many IRAT handoverdecisions are performed too early in source RAT 120, and may be used forautomatic or manual optimization of a cell configuration.

FIGS. 8 and 9 are flow charts of an example process 800 for detectingtoo early IRAT handover triggering in a telecommunication systemaccording to embodiments described herein. In one embodiment, one ormore steps of process 800 may be performed by UE 110. In otherembodiments, some or all of process 800 may be performed by anotherdevice or group of devices (e.g., communicating with UE 110).

As illustrated in FIG. 8, process 800 may include detecting poorcoverage of a source RAT connected to a UE (block 810), connecting theUE to a target RAT when poor coverage is detected (block 820), andmeasuring, for a time period, the source RAT after the UE connects tothe target RAT (block 830). For example, in embodiments described abovein connection with FIG. 5, UE 110 may initially be connected to sourceRAT 120 and may detect poor coverage in source RAT 120, as indicated byreference number 505. UE 110 may begin searching (e.g., viameasurements) for a target RAT with better coverage than source RAT 120,as indicated by reference number 510, and may identify target RAT 130based on the measurements. Source RAT 120 may receive a measurementreport (e.g., identifying target RAT 130 as a RAT with better coveragethan source RAT 120) and may generate an IRAT handover request (e.g.,requesting handover of UE 110 to target RAT 130) based on themeasurement report. Source RAT 120 may trigger an IRAT handover of UE110 (e.g., to target RAT 130), as indicated by reference number 530, andmay provide (e.g., after receiving an IRAT handover acknowledgement fromtarget RAT 130) an IRAT handover command to UE 110, as indicated byreference number 535. Based on the IRAT handover command, UE 110 mayconnect to target RAT 130, as indicated by reference number 540. UE 110may measure coverage associated with source RAT 120 for a period of time(e.g., which may be defined by a network administrator) after UE 110 isconnected to target RAT 130, as indicated by reference number 545.

As further shown in FIG. 8, process 800 may include sending, based onthe measurements, periodic measurement reports (or a single measurementreport) to the target RAT, where the target RAT forwards the measurementreport(s) to the source RAT for handling (block 840), and stopping themeasuring and the sending when the time period expires (block 850). Forexample, in embodiments described above in connection with FIG. 5, UE110 may provide a measurement report to target RAT 130, as indicated byreference number 550. The measurement report may be provided (e.g., byUE 110 to target RAT 130) together with a handover confirm message, asfurther indicated by reference number 550. Target RAT 130 may receivethe measurement report and may forward the measurement report to sourceRAT 120 (e.g., along with handover success message), as indicated byreference number 555. UE 110 may continue (e.g., for the period of time)to provide one or more additional measurement reports to target RAT 130,as indicated by reference number 560, and target RAT 130 may forward theone of more additional measurement reports to source RAT 120, asindicated by reference number 565. After the period of time expires, UE110 may stop measuring and/or reporting about the coverage associatedwith source RAT 120, as indicated by reference number 570.

Process block 820 may include the process blocks depicted in FIG. 9. Asillustrated in FIG. 9, process block 820 may include measuring one ormore other RATs to detect the target RAT with better coverage than thesource RAT (block 900), reporting the detection of the target RAT to thesource RAT (block 910), receiving, from the source RAT, a command tohandover the UE to the target RAT (block 920), and connecting the UE tothe target RAT based on the handover command (block 930). For example,in embodiments described above in connection with FIG. 5, UE 110 maybegin searching (e.g., via measurements) for a target RAT with bettercoverage than source RAT 120, as indicated by reference number 510, andmay identify target RAT 130 based on the measurements. UE 110 mayprovide a measurement report (e.g., identifying target RAT 130 as a RATwith better coverage than source RAT 120) to source RAT 120, as indictedby reference number 515. Source RAT 120 may receive the measurementreport and may generate an IRAT handover request (e.g., requestinghandover of UE 110 to target RAT 130) based on the measurement report.Source RAT 120 may trigger an IRAT handover of UE 110 (e.g., to targetRAT 130), as indicated by reference number 530, and may provide (e.g.,after receiving an IRAT handover acknowledgement from target RAT 130) anIRAT handover command to UE 110, as indicated by reference number 535.Based on the IRAT handover command, UE 110 may connect to target RAT130, as indicated by reference number 540.

FIG. 10 is a flow chart of another example process 1000 for detectingtoo early IRAT handover triggering in a telecommunication systemaccording to embodiments described herein. In one embodiment, one ormore steps of process 1000 may be performed by UE 110. In otherembodiments, some or all of process 1000 may be performed by anotherdevice or group of devices (e.g., communicating with UE 110).

As illustrated in FIG. 10, process 1000 may include detecting poorcoverage of a source RAT connected to a UE (block 1010), determining atarget RAT with sufficient coverage (block 1020), and receiving, fromthe source RAT and based on a handover request, a command to handoverthe UE to a target RAT, where the handover request includes one or bothof strength/quality thresholds for the source RAT (block 1030). Forexample, in embodiments described above in connection with FIG. 6, UE110 may initially be connected to source RAT 120 and may detect poorcoverage in source RAT 120, as indicated by reference number 605. UE 110may begin searching (e.g., via measurements) for a target RAT withbetter coverage than source RAT 120, as indicated by reference number610, and may identify target RAT 130 based on the measurements. SourceRAT 120 may provide an IRAT handover request to target RAT 130, asindicated by reference number 620. The IRAT handover request may includeone or both of strength/quality (e.g., a signal strength and/or a signalquality) thresholds for source RAT 120. Source RAT 120 may receive(e.g., based on the IRAT handover request) an IRAT handover requestacknowledgment from target RAT 130, as indicated by reference number625. Based on the IRAT handover request acknowledgment, source RAT 120may trigger an IRAT handover of UE 110 (e.g., to target RAT 130), asindicated by reference number 630, and may provide an IRAT handovercommand to UE 110, as indicated by reference number 635.

As further shown in FIG. 10, process 1000 may include connecting the UEto the target RAT based on the handover command (block 1040), measuring,for a time period, the source RAT after the UE connects to the targetRAT (block 1050), and sending, based on the measurements, periodicmeasurement reports (or a single measurement report) to the target RAT(block 1060). For example, in embodiments described above in connectionwith FIG. 6, based on the IRAT handover command, UE 110 may connect totarget RAT 130, as indicated by reference number 640. UE 110 may measurecoverage associated with source RAT 120 for a period of time (e.g.,which may be defined by a network administrator) after UE 110 isconnected to target RAT 130, as indicated by reference number 645. UE110 may provide a measurement report (e.g., based on the measurements)to target RAT 130, as indicated by reference number 650. The measurementreport may be provided (e.g., by UE 110 to target RAT 130) together witha handover confirm message, as further indicated by reference number650. UE 110 may continue (e.g., for the period of time) to provide oneor more additional measurement reports to target RAT 130.

Returning to FIG. 10, process 1000 may include receiving a handovercommand back to the source RAT when a strength/quality level of thesource RAT fulfills one or both of strength/quality conditions (e.g.,thresholds) for IRAT handover (block 1070), and stopping the measuringand the sending when the time period expires, (block 1080). For example,in embodiments described above in connection with FIG. 6, if themeasured signal strength and/or signal quality of source RAT 120 (e.g.,as provided by the measurement report(s)) satisfies the strength/qualitythresholds after IRAT handover of UE 110 to target RAT 130, target RAT130 may determine that the IRAT handover was performed too early. Basedon this determination, target RAT 130 may trigger IRAT handover of UE110 back to source RAT 120, as indicated by reference number 655. In oneexample, IRAT handover of UE 110 back to source RAT 120 (e.g., to thesame or a different network node of source RAT 120) may be triggeredindependently of a strength/quality level of target RAT 130. Target RAT130 may provide a handover command to UE 110, as indicated by referencenumber 660, and UE 110 may stop measuring and/or reporting about thecoverage associated with source RAT 120. UE 110 may then connect tosource RAT 120 (e.g., based on the handover command), as indicated byreference number 665. The receiving network node of source RAT 120 mayinform a network node in source RAT 120 (e.g., responsible for statisticcollection and optimization) that an IRAT handover was triggered tooearly, as indicated by reference number 670.

FIG. 11 is a flow chart of still another example process 1100 fordetecting too early IRAT handover triggering in a telecommunicationsystem according to embodiments described herein. In one embodiment,process 1100 may be performed by UE 110. In other embodiments, some orall of process 800 may be performed by another device or group ofdevices (e.g., communicating with UE 110).

As illustrated in FIG. 11, process 1100 may include detecting poorcoverage of a source RAT connected to a UE (block 1110), determining atarget RAT with sufficient coverage (block 1120), and receiving, fromthe source RAT and based on a handover request, a command to handoverthe UE to a target RAT, where the handover request includes one or bothof strength/quality thresholds for the source RAT (block 1130). Forexample, in embodiments described above in connection with FIG. 7, UE110 may initially be connected to source RAT 120 and may detect poorcoverage in source RAT 120, as indicated by reference number 705. UE 110may begin searching (e.g., via measurements) for a target RAT withbetter coverage than source RAT 120, as indicated by reference number710, and may identify target RAT 130 based on the measurements. SourceRAT 120 may provide an IRAT handover request to target RAT 130, asindicated by reference number 720. The IRAT handover request may includestrength/quality (e.g., a signal strength and/or a signal quality)thresholds for source RAT 120. Source RAT 120 may receive (e.g., basedon the IRAT handover request) an IRAT handover request acknowledgmentfrom target RAT 130, as indicated by reference number 725. Based on theIRAT handover request acknowledgment, source RAT 120 may trigger an IRAThandover of UE 110 (e.g., to target RAT 130), as indicated by referencenumber 730, and may provide an IRAT handover command to UE 110, asindicated by reference number 735.

As further shown in FIG. 11, process 1100 may include connecting the UEto the target RAT based on the handover command (block 1140), measuring,for a time period, the source RAT after the UE connects to the targetRAT (block 1150), and sending, based on the measurements, periodicmeasurement reports (or a single measurement report) to the target RAT(block 1160). For example, in embodiments described above in connectionwith FIG. 7, based on the IRAT handover command, UE 110 may connect totarget RAT 130, as indicated by reference number 740. UE 110 may measurecoverage associated with source RAT 120 for a period of time (e.g.,which may be defined by a network administrator) after UE 110 isconnected to target RAT 130, as indicated by reference number 745. UE110 may provide a measurement report (e.g., based on the measurements)to target RAT 130, as indicated by reference number 750. The measurementreport may be provided (e.g., by UE 110 to target RAT 130) together witha handover confirm message, as further indicated by reference number750. UE 110 may continue (e.g., for the period of time) to provide oneor more additional measurement reports to target RAT 130.

Returning to FIG. 11, process 1100 may include the target RAT providinga too early handover indication to the source RAT when astrength/quality level of the source RAT fulfills one or both ofstrength/quality conditions (e.g., thresholds) for IRAT handover (block1170), and stopping the measuring and the sending when the time periodexpires (block 1180). For example, in embodiments described above inconnection with FIG. 7, target RAT 130 may receive the one or moremeasurement reports, and may compare the measurement report(s) to one orboth of strength/quality (e.g., a signal strength and/or a signalquality) thresholds. If the measured signal strength and/or signalquality of source RAT 120 (e.g., as provided by the measurementreport(s)) satisfies the strength/quality thresholds after IRAT handoverof UE 110 to target RAT 130, target RAT 130 may determine that the IRAThandover was performed too early. Based on this determination, targetRAT 130 may generate a too early IRAT handover indication, as indicatedby reference number 755, and may provide the too early IRAT handoverindication to source RAT 120, as indicated by reference number 760. UE110 may stop measuring and reporting signal strength and/or signalquality associated with source RAT 120.

Systems and/or methods described herein may provide mechanisms to detecttoo early IRAT handover triggering (e.g., which was previouslyundetectable) and to mitigate too early IRAT handover triggering in thefuture. The systems and/or methods may enable automatic or manual tuningof IRAT handover parameters of a source RAT to minimize the number ofhandovers triggered too early, which may result in a more efficient cellconfiguration. The systems and/or methods may instruct a UE (e.g., forwhich an IRAT handover, from a source RAT to a target RAT, wasperformed) to continue measuring the source RAT and the target RAT for atime period after the IRAT handover. The systems and/or methods mayinstruct the UE to send a measurement report (e.g., based on themeasurements of the source and target RATs) to the target RAT after thetime period expires. Upon reception of the measurement report, thetarget RAT may forward the measurement report to the source RAT.Alternatively, or additionally, the target RAT may trigger a second IRAThandover to the source RAT even if a poor coverage threshold (e.g., fortriggering IRAT handover) is not satisfied.

The foregoing description of embodiments provides illustration anddescription, but is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Modifications and variationsare possible in light of the above teachings or may be acquired frompractice of the invention.

For example, while series of blocks have been described with regard toFIGS. 5-11, the order of the blocks may be modified in otherembodiments. Further, non-dependent blocks may be performed in parallel.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

It will be apparent that aspects, as described above, may be implementedin many different forms of software, firmware, and hardware in theembodiments illustrated in the figures. The actual software code orspecialized control hardware used to implement these aspects should notbe construed as limiting. Thus, the operation and behavior of theaspects were described without reference to the specific softwarecode--it being understood that software and control hardware could bedesigned to implement the aspects based on the description herein.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the invention. In fact, many of these features may becombined in ways not specifically recited in the claims and/or disclosedin the specification.

No element, block, or instruction used in the present application shouldbe construed as critical or essential to the invention unless explicitlydescribed as such. Also, as used herein, the article “a” is intended toinclude one or more items. Where only one item is intended, the term“one” or similar language is used. Further, the phrase “based on” isintended to mean “based, at least in part, on” unless explicitly statedotherwise.

What is claimed is:
 1. A method in a source radio access technology(RAT) network node for detecting a too early triggered inter-RAThandover of a user equipment from the source RAT network node to atarget RAT network node, the method comprising the steps of: sendingmeasurement configuration information to the target RAT network node forinstructing the user equipment to measure the source RAT during a periodof time while being connected to the target RAT; and receiving from thetarget RAT network node a too early inter-RAT handover report based onthe user equipment measurements of the source RAT.
 2. The method ofclaim 1, wherein the measurement configuration information includes oneor both of a signal strength threshold and a signal quality threshold.3. The method of claim 2, wherein the one or both of the signal strengththreshold and the signal quality threshold sent by the source RATnetwork node to the target RAT network node in the measurementconfiguration information is configured to cause the target RAT networknode to send the too early inter-RAT handover report when the userequipment measurements of the source RAT exceeds the one or both of thesignal strength threshold and the signal quality threshold.
 4. Themethod of claim 2, wherein sending measurement configuration informationto the target RAT network node, comprises sending the one or both of thesignal strength threshold and the signal quality threshold in a handoverrequest associated with the inter-RAT handover.
 5. The method of claim2, wherein sending measurement configuration information to the targetRAT network node, comprises sending the one or both of the signalstrength threshold and the signal quality threshold in a message that isseparate from a handover request associated with the inter-RAT handover.6. The method of claim 2, wherein sending measurement configurationinformation to the target RAT network node, comprises sending the one orboth of the signal strength threshold and the signal quality thresholdin a handover request associated with a handover occurring before theinter-RAT handover.
 7. The method of claim 1, further comprising thestep of tuning at least one inter-RAT handover parameter based on thereceived too early inter-RAT handover report.
 8. A source radio accesstechnology (RAT) network node for detecting a too early triggeredinter-RAT handover of a user equipment from the source RAT network nodeto a target RAT network node, the source RAT network node beingconfigured to: send measurement configuration information to a targetRAT network node for instructing the user equipment to measure thesource RAT during a period of time while being connected to the targetRAT; and receive from the target RAT network node a too early inter-RAThandover report based on the user equipment measurements of the sourceRAT.
 9. The source RAT network node of claim 8, wherein the measurementconfiguration information includes one or both of a signal strengththreshold and a signal quality threshold.
 10. The source RAT networknode of claim 9, wherein the one or both of the signal strengththreshold and the signal quality threshold sent by the source RATnetwork node to the target RAT network node in the measurementconfiguration information is configured to cause the target RAT networknode to send the too early inter-RAT handover report when the userequipment measurements of the source RAT exceeds the one or both of thesignal strength threshold and the signal quality threshold.
 11. Themethod of claim 10, wherein sending measurement configurationinformation to the target RAT network node, comprises sending the one orboth of the signal strength threshold and the signal quality thresholdin a handover request associated with the inter-RAT handover.
 12. Themethod of claim 10, wherein sending measurement configurationinformation to the target RAT network node, comprises sending the one orboth of the signal strength threshold and the signal quality thresholdin a message that is separate from a handover request associated withthe inter-RAT handover.
 13. The method of claim 10, wherein sendingmeasurement configuration information to the target RAT network node,comprises sending the one or both of the signal strength threshold andthe signal quality threshold in a handover request associated with ahandover occurring before the inter-RAT handover.
 14. The source RATnetwork node of claim 8, further configured to tune at least oneinter-RAT handover parameter based on the received too early inter-RAThandover report.